1. Field of the Invention
The present invention relates to a developing device provided in an electrophotographic recorder.
2. Description of the Related Art
An electrophotographic recorder used as a copying machine, a facsimile, a laser printer, etc. has a charger, an exposure device, a developing device, a transfer device and a fixing device sequentially arranged around a photosensitive drum in its rotating direction. In the operation of the recorder, the photosensitive drum is firstly operated to rotate, the charger charges the surface of the rotating drum, the exposure device exposes the charged surface of the rotating drum to form a latent image, the developing device develops the latent image on the surface of the rotating drum with toner to form a toner image, the transfer device transfers the toner image from the surface of the drum to a recording sheet, and the fixing device fixes the toner image on the recording sheet to record the image on the recording sheet.
The developing device provided in the electrophotographic recorder stores toner in its device body and supplies toner from the device body to the surface of the photosensitive drum. When the toner in the device body is reduced upon use of the toner, toner is supplied into the device body. In one method to supply toner into the device body of the developing device, an exchangeable toner cartridge is used. The toner cartridge storing toner is mounted in the device body and supplies toner into the device body. When the amount of the toner in the device body is reduced below a predetermined value, the toner cartridge is removed from the device body, and a new one is mounted in the device body.
A developing device of a toner cartridge exchange type is constructed as described below. A toner reception port is formed on the upper surface of the device body, and guide rails are provided at both side edges of the toner reception port. Each guide rail has a hook-shaped cross-section, and the guide rails retain both side edges of the toner cartridge from lateral sides and above. A toner discharge port is formed on the lower surface of the toner cartridge. The toner discharge port of the toner cartridge is, for example, sealed by bonding a strip-like sheet.
In mounting operation of the toner cartridge, the toner cartridge is placed on the upper surface of the device body so as to associate both of its side edges with the guide rails and to support both side edges of the toner cartridge with the guide rails from the lateral sides and above. The toner cartridge is then slid along the guide rails to the toner reception port, so that the toner cartridge is mounted in the device body. The externally projected end of the strip-shaped sheet is finally pulled to separate the strip-shaped sheet from the toner cartridge, so that the toner discharge port is opened. Toner stored in the toner cartridge is discharged from the opened toner discharge port into the device body through the toner reception port.
When the toner in the device body needs to be replenished, the empty toner cartridge mounted in the device body is removed from the device body and a new toner cartridge is mounted in the device body. According to this toner cartridge exchange type, toner stored in the toner cartridge can be supplied into the device body without leakage, so that the contamination of scattered toner is prevented.
When the toner cartridge is mounted in the device body in the developing device of the toner cartridge exchange type, if a gap exists between the upper surface of the device body and the lower surface of the toner cartridge, toner in the device body is leaks out through the gap. Therefore, sealing means is provided between the device body and the toner cartridge so as to prevent the gap from being produced therebetween.
A gasket made of sponge and the like is usually disposed on the upper surface of the device body so as to function as the sealing member. When the toner cartridge is placed on the gasket to be mounted in the device body, the gasket seals between the device body and the toner cartridge to prevent the gap from being produced therebetween.
However, the developing device of the conventional toner cartridge type has following various problems.
In the conventional developing device as described above, in order to mount the toner cartridge in the device body, the toner cartridge is placed on the gasket disposed on the upper surface of the body to insert the side edges of the toner cartridge into the pair of guide rails formed in the device body and to retain both side edges of the toner cartridge from above by the guide rails. The toner cartridge is then slid along the guide rails to coincide with the toner reception port of the device body.
In order to securely bring the lower surface of the toner cartridge into close contact with the gasket disposed in the device body, it is necessary to press the gasket from above with the toner cartridge. For this reason, the height of the guide rails for retaining the toner cartridge is so regulated that the toner cartridge is retained from above by the guide rails at a position in which the gasket is compressed in a predetermined value by the toner cartridge.
With the above described conventional construction, while side edges of the toner cartridge are interposed between the guide rails and the gasket reaction force generated upon compression of the gasket is applied to the both side edges of the toner cartridge.
Therefore, a strong frictional force is applied to the toner cartridge when the toner cartridge is slidably inserted into and discharged from the guide rails. In order to slide the toner cartridge against the strong frictional force, the mounting and removing operation of the toner cartridge to and from the device body needs strong force and the strong force makes the above operation troublesome.
In order to ease the above operation, it is considered that the compression amount of the gasket by the toner cartridge is reduced. In this case, when the toner cartridge is inserted into the guide rails in a state that the toner cartridge is inclined to the guide rails due to the dimensional difference of the guide rails and the cartridge in the production, a gap may be generated between the toner cartridge and the guide rails so that the sealability between the toner cartridge and the device body becomes insufficient.